June 24, 1904.] 



SCIENCE. 



941 



Fischex- and recompared with the stand- 

 ards of the international bureau. 



It will be remembered that in 1893 con- 

 gress adopted the international meter as 

 the fundamental unit of length, continuing 

 the ratio of the yard to the meter as 36 to 

 39.37. At the same time the international 

 kilogram was adopted as the fundamental 

 unit of mass. Thus the old standard yard 

 of 1840 and the troy pound of the mint of 

 1827 were superseded, and hence all meas- 

 ures of length and mass in either metric or 

 English system are now referred to the 

 international meter and kilogram. 



"VVe are at present prepared to determine 

 the length of any standard from 1 deci- 

 meter to 50 meters, and also to calibrate the 

 subdivisions of such standards and to de- 

 termine the coefficient of expansion of the 

 same for ordinary ranges of temperature. 

 .The bureau is also prepared at the pres- 

 ent time to compare base-measuring ap- 

 paratus and steel tapes, but the facilities 

 are such that the best resultsi are only 

 attained at the expense of great labor. 



The tunnel connecting the physical and 

 mechanical laboratories will be fitted out 

 with facilities for comparing this kind of 

 apparatus. This tunnel will be 170 feet 

 long, 7 feet wide and 8 feet high, and 

 facilities will be provided for comparing 

 tapes up to 50 meters in length and to lay 

 out a base of the same length with an error 

 not greater than one part in two or three 

 million, over which base-measuring ap- 

 paratus may be tested. Means will also be 

 provided for raising the temperature to, 

 say, 40° Centigrade, and lowering to 10° 

 C, for the determination of temperature 

 coefficients of apparatus submitted. 



The bureau possesses two iridio-platinum 

 copies of the international kilogram and 

 also the necessary working standards to 

 verify masses from 0.1 milligram . to 20 

 kilograms. The balances now on hand in- 

 clude a series of the best American makes 



and one precision balance similar to those 

 found at the International Bureau of 

 Weights and Measures. These are to be 

 supplemented by other precision balances 

 now being constructed, and when the phys- 

 ical building is completed and the balances 

 installed the determination of masses 

 within the above-named range may be 

 made with the highest degree of accuracy. 



The determination of the density of 

 solids and of liquids is also part of the 

 work of this section. Two sets of Jena 

 glass hydrometers, graduated to read densi- 

 ties directly from 0.6 to 2.0, and verified at 

 the Normal-Aichungs Kommission of Ber- 

 lin, form part of the newer apparatus of 

 this section. 



Capacity measures from 1 milliliter to 

 40 liters are being standardized, and plans 

 are being made to test various kinds of 

 chemical measuring apparatus in large 

 quantities. 



Aneroid barometers are also tested by 

 this section, employing the very convenient 

 apparatus designed by Dr. Hebe of the 

 Reichsanstalt and vised at that institution. 



The bureau has also been called upon to 

 advise the officers of state and city sealers 

 of weights and measures regarding the 

 proper equipment of those officers and the 

 methods to be pursued in performing their 

 functions. 



Section 2. Thermometry and Pyrom- 

 e^rj/.— Facilities have now been provided 

 for the testing of mercurial thermometers 

 in the interval — 30° C. to + 550° C. The 

 testing of toluene, petroleum-ether and 

 pentane thermometers, and copper eon- 

 stantan thermocouples for low temperature 

 work, will be undertaken in the near fu- 

 ture, the range extending down to about 

 - 200° C. 



The standard scale of temperature 

 ■adopted by this bureau for work in the 

 interval — 30° to + 100° C. is the scale of 

 the hydrogen gas thermometer, as defined 



